May 30, 2005
Erica Hupp
Headquarters, Washington
(Phone: 719/649-8469)
Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
(Phone: 617/721-6757)
RELEASE: 05-136
NASA SEES ORBITING STARS FLOODING SPACE WITH GRAVITATIONAL WAVES
A scientist using NASA's Chandra X-ray Observatory has found evidence
that two white dwarf stars are orbiting each other in a death grip,
destined to merge.
The data indicate gravitational waves are carrying energy away from
the star system at a prodigious rate, making it a prime candidate for
future missions designed to directly detect these ripples in
space-time.
Einstein's General Theory of Relativity predicted a binary star system
should emit gravitational waves that rush away at the speed of light
and cause the stars to move closer together. As the stars move closer
together, the orbital period decreases, and it can be measured by
Chandra. The orbital period of this system is decreasing by 1.2
milliseconds every year. This is a rate consistent with the theory
that predicted loss of energy due to gravitational waves.
The system is known as RX J0806.3+1527 or J0806. The white dwarf pair
in J0806 might have the smallest orbit of any known binary system.
The stars are only about 50,000 miles apart, a fifth of the distance
from the Earth to the moon. As the stars swirl closer together,
traveling in excess of one million mph, the production of
gravitational waves increases.
"If confirmed, J0806 could be one of the brightest sources of
gravitational waves in our galaxy," said Tod Strohmayer of NASA's
Goddard Space Flight Center, Greenbelt, Md. He presented data today
at the American Astronomical Society meeting in Minneapolis. "It
could be among the first to be directly detected with an upcoming
space mission called LISA, the Laser Interferometer Space Antenna,"
he added.
White dwarfs are remnants of stars that have used up all their fuel.
Along with neutron stars and black holes, white dwarfs are called
compact objects, because they pack a lot of mass into a small volume.
The white dwarfs in the J0806 system each have an estimated mass of
one-half the sun, yet are only about the size of Earth.
Optical and X-ray observations of J0806 showed periodic variations of
321.5 seconds, barely more than five minutes. The observation in
J0806 is most likely the orbital period of the white dwarf system.
However the possibility that it represents the spin of one of its
white dwarfs cannot be completely ruled out.
"It's either the most compact binary known or one of the most unusual
systems we've ever seen. Either way it's got a great story to tell,"
Strohmayer said.
Strohmayer's Chandra X-ray observations tighten orbital decay
estimates made through optical independent observations by other
research teams. Strohmayer's data will be published in an upcoming
issue of The Astrophysical Journal.
NASA's Marshall Space Flight Center, Huntsville, Ala., manages the
Chandra program for NASA's Science Mission Directorate. The
Smithsonian Astrophysical Observatory controls science and flight
operations from the Chandra X-ray Center in Cambridge, Mass.
For additional Chandra information and images on the Internet, visit:
http://chandra.nasa.gov
http://chandra.harvard.edu
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